1. Field of the Invention
This invention relates broadly to mechanisms for igniting fuel in a combustion chamber. More particularly, this invention relates to ignitor plugs that utilize resistive heating to ignite a liquid fuel supplied thereto for generating a flame that ignites fuel in a combustion chamber.
2. State of the Art
It is common for small size turbine engines and other small rotary engines to employ an ignitor plug that utilizes resistive heating to ignite a combustible gas fuel supplied thereto for generating a flame that ignites fuel in a combustion chamber. When the combustion chamber has been heated sufficiently, heavy liquid fuel is introduced and ignited by the hot flame in the combustion chamber. At that time the gas fuel to the ignitor plug is shut off and the engine continues to run on the heavy liquid fuel supplied to the combustion chamber. Such an ignitor plug is typically referred to as a glow plug. Examples of glow plugs are those sold commercially under the trade name O.S. Engines by Great Planes Model Distributors of Champaign, Ill. However, the resistive heating employed by the prior art glow plugs will not ignite heavy liquid fuels that are required to run the engine. This requires the incorporation of an additional gas fuel system to start the engine. The additional gas fuel system significantly increases the operational cost and weight of such engines.
Glow plugs which vaporize and ignite heavy fuel have been utilized in large diesel engines to heat the combustion air to aid in starting the engine. However, these prior art glow plugs typically use high amperage D.C. voltages and are very large and heavy. In addition, they are subject to coking of the fuel path through the glow plug. Such coking significantly reduces the operational lifetime of the glow plug and increases the operational costs of such engines. Moreover, these glow plugs are not compatible with small-size turbine engines.
Therefore, there remains a need in the art for an improved lightweight, low-amperage, low cost glow plug and starting systems based thereon that are suitable for small-size turbine engines and that are not susceptible to fuel coking.